"Look at what's happening in the Middle East as a result of some of the material we've been publishing."

David House, a friend who regularly visits Manning in prison, told the programme that he believed the US was trying to force the former US intelligence analyst into bringing down Assange.

Manning is allowed out of his cell for only one hour a day for exercise outside or at an indoor gym, he said.

"In terms of Bradley Manning's case, it's very clear the US government is trying to crack him open with solitary confinement by causing emotional devastation," House told ITV.

"They're trying to get him to issue a confession, or false confession, so they can link him to Julian Assange," he added.

US military authorities brought additional charges against Manning on Wednesday, accusing him of illegally downloading vast numbers of secret government files and "aiding the enemy."

Pentagon press secretary Geoff Morrell denied Manning was being mistreated, saying Thursday: "There's 30 people on a U-shaped corridor, so he's not in a hole. He's not away from others. He's allowed to have conversations with others on that corridor."